As background for our invention reference can be had to pulsed fluid motion as described by Perkins, Ktra, Stephanoff, and Murray. A detailed description can be found in Vol. 12, No. 4 of the IEEE Transactions on Components, Hybrids, and Manufacturing Technology, dated December 1989. Basically the flow described by Perkins, et. al. contains two parts, a steady state component and an oscillatory component. The oscillation is such that there is always a net velocity in the same direction. This type of flow in an electronics cavity tends to periodically replace fluid trapped within small cavities such as between modules. As a result of this periodic motion of the fluid, local velocities in the cavities are higher than compared with steady state flow.
This article describes the process by which heat transfer rates are increased, however it does not say how this motion is to be generated. It does say that a positive net airflow is required to carry the heat away.
One possible technique to obtain pulsed flow is to use a breathing cooling system. This has been described by Dr. Victor Nee of the University of Notre Dame. In this scheme a pivoted baffle is turned back and forth repeatedly. Airflow is constantly accelerating, thereby achieving local heat transfer gains as described by Perkins. However, this technique suffers from the fact that the net flow is approximately zero. For modest power dissipations the air temperature rise will overpower the gains realized in heat transfer coefficient. A fan will be needed in addition to the breathing device in order to cool the electronics system. It is not clear how the fan and breathing system will interact because the breathing system will generate a large amount of pressure which may overpower some fans. Moreover, two air circuits may be required instead of just one.
Dr. Nee disclosed his work to others, but we have found no publication or patent related to this work.
The patent art about baffles does not seem to be particularly applicable to our oscillating baffle concept.
German Patent No. 722860, dated Jul. 23, 1942, has a sketch which appears to show using a moveable baffle to alter the path of a fluid. From the sketch it appears as though the purpose of the baffles are to redirect mass flow to completely different sources at different points in time. This method appears to be a control scheme and not an augmentation to heat transfer.
The purpose of Japanese patent number 2-54998, dated February 1990, entitled "Air-Cooling Fan Unit," is to provide an easy means to control the airflow that passes over electronics. This method uses the concept of higher velocity and more airflow to achieve higher rates of heat transfer. We note that in this method the more cooling airflow that is delivered to one hot spot will means that less airflow is delivered to another. No mention is made of using added turbulence to increase the rate of heat transfer.
The purpose of Japanese patent number 1-297892, dated November 1989, entitled "Air Guiding Apparatus for Cabinet," is to control the mass flow through an electronic enclosure. This concept uses a variable baffle that can be rearranged to direct volumes of airflow through an enclosure. This concept could be useful for design, where many packages of a similar type are used. The method is primarily concerned with controlling the inlet and outlet airflow conditions within an enclosure and not with the rate of heat transfer imposed by the changed baffles.
The purpose of Japanese patent number 1-129497, dated May 1989, entitled "Cooling System for LSI Element of Electronic Equipment," is to control the rate of heat transfer by varying the airflow rate as a function of inlet or outlet air temperature. This patent does not mention the use of increased turbulence created by the baffle to augment heat transfer.
The purpose of Japanese patent number 57-167178, dated October 1982, entitled "Driving Method of Magnetic Disk Device," is to obtain uniform temperature fields on start up of magnetic disk. This patent does not use an oscillating type of flow, nor does it discuss augmentation of heat transfer via increased turbulence.
The purpose of Japanese patent number 55-68162, dated December 1981, entitled "Entilating System," is to baffle the airflow generated in a magnetic disk. This system augments heat transfer by increasing the rate of airflow by capturing and saving that airflow. No method of adding turbulence is discussed, other than just increasing the rate of flow.
The purpose of Japanese patent number 55-157173, dated December 1980, entitled "Magnetic Disc Device," is to maintain a uniform temperature distribution surrounding a Magnetic disc. The system employs a rotating baffle relative to the disc, however, the mixing of airflow is taking place in the baffle and not on the disc. The thermal boundary layer set up is steady state in nature. No mention is made of augmentation of heat transfer to lower the temperature but to make the air temperature distribution uniform. Moreover, the airflow is not pulsed to obtain this mixing, a specially designed airflow guide is used to push airflow through the disc.
The purpose of Japanese patent number 56-145573, dated November 1981, entitled "Disc Device for Computer or the Like," is to circulate airflow through an air filter. No mention is made of any augmentation to the rate of heat transfer via added turbulence.
The purpose of U.S. Pat. No. 4,648,007, dated Mar. 3, 1987, entitled "Cooling Module for Electronic Equipment," is to create a system of baffles that enable a system to receive cooling airflow when a fan has failed. No mention is made of augmenting the rate of heat transfer by increasing the turbulence.
The purpose of U.S. Pat. No. 3,812,534, dated May 21, 1974, entitled "Ventilation Device for a Magnet Disk Unit," is to allow a vent for a disk unit that does not allow contaminated airflow to enter. The patent discusses a situation in which there is a pulsating airflow, however, there is no description of how that airflow assists in heat transfer.